2. Make brownies: melt butter in a large heavy-bottomed pot over medium heat. Reduce heat to low and add baking chocolate. Stir until chocolate has melted. Remove pot from heat. Add sugars and stir until incorporated into butter and chocolate. Let mixture cool for 10 minutes.

3. Crack eggs into a medium-sized bowl. Beat with a fork. Add salt and vanilla extract to the eggs and stir to combine. Pour beaten eggs into cooled chocolate mixture and stir together.

4. Mix flour, cocoa powder and baking powder in a large bowl. Add flour mixture to chocolate mixture and stir until a thick batter forms.

5. Grease a 18-by-13-inch sheet pan with butter. Line bottom of sheet pan with parchment paper and grease top of parchment paper. Lightly flour. Pour batter onto the sheet pan and spread in an even layer. Bake for 25 minutes.

6. Make frosting: Place butter in a stand mixer. Add confectioners’ sugar, 4 tablespoons of whipping cream, vanilla and salt. Turn mixer on low until the sugar is incorporated, then increase speed to medium and mix until a thick frosting forms.

7. Melt chocolate chips over a double boiler. With mixer running on low, pour warm melted chocolate into the frosting. Mix until chocolate is incorporated into the frosting. Increase speed to medium. Beat until frosting is fluffy, adding 1 to 2 tablespoons of whipping cream, if needed. Immediately frost cooled brownies. Let frosting set for an hour before wrapping in plastic wrap. Cut into squares before serving.